Make the citrus spice:
Dry the citrus rinds; place them on a paper towel, and microwave for 3 minutes in increments of 30 seconds, till the rinds are shriveled and dry. Crush the dried pieces using a pestle & mortar, along with the fennel and chili flakes to form a coarse mixture. Alternatively, blitz using a food processor, a hand blender, or a coffee grinder. Add the ground cinnamon and nutmeg, and mix well.
Cut the chicken into 1-inch wide strips and season with salt, pepper, and the citrus spice. Drizzle the freshly squeezed lime and orange juice, and let the chicken marinate for at least 20 minutes.
In the skillet, heat the ghee over medium-high heat. Cook the chicken on each side for 3 minutes, till it is slightly charred. Transfer to a plate and garnish with cilantro, spinach, and lime and orange slices.